This invention relates to apparatus for treating gases with liquids, such as removing solid and liquid contaminants from gases, for example, for removing paint particles, fiber glass, grinding dust, enamel and porcelain frit, and the like, from air which has been moved through a working area for ventilation purposes. The invention is particularly applicable to paint spray booths, and is discussed herein in that particular context. However, it is to be understood that the invention has broad application as first above stated.
Various systems have been devised to remove contaminant material from air, one of the more common being a water wash system wherein water is flowed downwardly over an imperforate wall at the rear of a work area and across an air gap adjacent the floor of the work area, thereby providing a flow of water through which air is drawn at high velocity. Such systems, however, have not been completely effective for all contaminant material or for all particle sizes of material which are to be removed from the air.
In an attempt to increase efficiency, other systems, such as disclosed in U.S. Pat. Nos. 1,138,081 and 1,966,280, utilized a plurality of water sprays followed by a filter. Still others moved the air through water sprays followed by an intricate series of baffles which purported to separate the water and contaminants from the air, such for example as Clark et al U.S. Pat. No. 2,395,960, Gallagher U.S. Pat. No. 3,119,675 and French Pat. No. 1,192,088. These systems also proved to be less efficient than was desirable in removing contaminants and, furthermore, allowed too great an amount of moisture to remain in the air as it is exhausted to atmosphere.
Another scheme to increase efficiency was to increase the turbulence by the utilization of fine droplets or by spiraling the air flow through the water spray. Examples of this concept are shown, for example, in Hoffman et al U.S. Pat. No. 3,641,743 and McCornack U.S. Pat. No. 2,047,424.
It is believed that the inefficiency of the above-mentioned systems results from (1) utilization of large wash areas wherein the air cannot be effectively scrubbed and/or (2) utilization of sprays in the form of scattered droplets which, even under violent agitation, do not wet the contaminant particles. The particles, therefore, tend to remain in the air rather than be picked up by the water.
Attempts to solve the problem by use of restricted wash areas appear in (1) Campbell U.S. Pat. No. 2,732,909 which discloses a restricted chamber wherein the air is subjected to a violent whirling action; (2) Panzica et al U.S. Pat. No. 3,328,009 wherein the air is drawn through a restricted chamber in which water is sprayed into a rapidly rotating cage to break the water up into droplets in a pattern confined to the spray chamber; (3) Arnold U.S. Pat. No. 3,737,106 wherein a nozzle ejects water against a deflector to produce a radial spray in a cylindrical chamber; (4) Larsson et al U.S. Pat. No. 3,138,087 and Wilhelmsson et al U.S. Pat. No. 3,168,030 wherein an elongated slot is formed by converging water washed subfloors, and the water is atomized at the slot by means of a venturi formation acting on the water and paint laden air as they are discharged through the slot; (5) Gallagher U.S. Pat. Nos. 3,119,675 and 3,782,080 wherein the air is drawn through a cylindrical opening and against a baffle opposed to the outlet of the opening, the air passing through a spray of small droplets of washing liquid as it moves through the opening; (6) Fisher U.S. Pat. No. 2,337,983 wherein nozzles direct a powerful spray of water through a plurality of venturi tubes, the sprays being powerful enough to induce air flow through the tubes to pull contaminated air and fumes therethrough, and wherein vaned cones at the lower end of each tube produce a churning air washing action in the spray which is discharged into a chamber located beneath the tubes; and (7) Halls U.S. Pat. No. 3,421,293 wherein a plurality of upright tubes, mounted in a water-washed floor beneath a spray booth, are provided with vanes to produce gyratory turbulence in the air and water as they are discharged through the tubes.
While providing various advantages, these devices have not proven to be entirely satisfactory in removing contaminant particles from the air, particularly under increasingly strict standards for environmental protection.